1. Field of the Invention
The present invention relates to an active matrix type display device using light emitting elements as pixels and a driving method thereof. The present invention relates also to an electronic apparatus in which this type of display device is assembled.
2. Description of Related Art
The development of emissive, flat panel display devices using an organic electroluminescent (EL) device as an optical emitting element has been made vigorously in recent years. An organic EL device is a device utilizing a phenomenon in which as an electric field is applied to an organic thin film, light emission occurs. Since the organic EL device is driven by an application voltage of 10 V or lower, the device consumes a low power. Since the organic EL device is an emissive device which emits light by itself, no illumination member is required and the device can be made light in weight and thin easily. Furthermore, a response time of the organic EL device is very fast, at about several ms, so that an afterimage does not occur during the display of moving images.
Among flat panel emissive type display devices using organic EL devices as pixels, active matrix type display devices integrating a thin film transistor in each pixel have been developed vigorously. Active matrix type, flat panel emissive display devices are described, for example, in the following Patent Documents 1 to 5.
Japanese Patent Application Publication No. 2003-255856 (Patent Document 1)
Japanese Patent Application Publication No. 2003-271095 (Patent Document 2)
Japanese Patent Application Publication No. 2004-133240 (Patent Document 3)
Japanese Patent Application Publication No. 2004-029791 (Patent Document 4)
Japanese Patent Application Publication No. 2004-093682 (Patent Document 5)
However, current-technology active matrix type, flat panel emissive display devices have a variation in threshold voltages and mobilities of transistors for driving light emitting elements due to process variations. The characteristics of an organic EL device are subject to a secular change. A variation in the characteristics of driver transistors and a change in the characteristics of organic EL devices affect an emission luminance. In order to control an emission luminance uniformly over the whole screen of a display device, a change in the characteristics of transistors and organic EL devices are required to be corrected in each pixel circuit. A display device provided with a correction function has been proposed. However, the proposed pixel circuit provided with the correction function requires a wiring for supplying an electrical potential for correction, switching transistors, and switching pulses, resulting in a complicated pixel circuit. Since there are many constituent elements of a pixel circuit, these elements hinder a high precision display.